Development of Scanning Probe Lithography (SPL)

EE C235/NSE C203 Nanofbrication

Jun Suk Rho

1) “Device fabrication by scanned probe oxidation”, Science, 19952) “Nanofabrication by scanning probe microscope lithography: A review”, J. Vac.

Sci. Tech., 20053) “Scanning Probe Parallel Nanolithography with Multiprobe CantileverArray Fabricated by Bulk Silicon Micromachining”, IEEJ, 2008

Group I.P.ODec. 5th 2007

Scanning Probe Lithography

Bottom Up Technique - Chemical and molecular patterning (DPN)Top down Technique - Mechanical Patterning• Scratching• Nano Indentation- Voltage bias application• Field Enhanced Oxidation• Electron exposure of resist materials

Substitution Technique - Manipulation of nanostructures

Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Achievements

Dec. 10th. 2008Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Scanning Probe Lithography (SPL)

Atomic Force Microscopy (AFM)

Scanning Tunneling Microscopy (STM)

Scanning Probe Parallel Lithography(SPL Array)

Dec. 10th. 2008Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Scanning Probe Lithography (SPL)

• Began at NIST in 1989• Typical line width: below 50nm• Scan rate: 10~20um/s• Creating patterns with high resolution but are

limited in throughputJ. A. Dagata, Vol. 270, pp1625-1626, Science, 1995

Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

AFM Lithography Scratching

Dec. 10th. 2008

The advantages of nanoscratching for lithography - The absence of additional processing steps (i.e etching)

Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Electric Field Enhanced Oxidation

Dec. 10th. 2008

• Voltage bias between a sharp probe tip and sample generates an intense electric field at the tip- Oxidization of silicon & Anodization of metals• The high field desorbs the hydrogen on the silicon surface and enables exposed silicon to oxidize• Oxidation depends on humidity• Can achieve sub-50nm feature sizes

J. A. Dagata, Vol. 270, pp1625-1626, Science, 1995Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Scanned Probe Oxidation- Applications

Fabrication of Si nanowire Fabrication of single tunneling transistor(SET)

J. A. Dagata, Vol. 270, pp1625-1626, Science, 1995Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Electric Field Enhanced Oxidation

Dec. 10th. 2008

AFM anodic Oxidation (Left)

AFM Nanolithography (Below)

Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Parallel Field Enhanced Oxidation

Dec. 10th. 2008Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Profile vs. Resist by AFM Lithography

M. Rolandi et al. NANO LETTERS. 2004 Vol. 4, No. 5 889-893Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Non Contact AFM Lithography

Dec. 10th. 2008

• Silicon probe tip acts as a source of electrons• The field emission current from the tip is used as the feedback signal to control the tip sample spacing

Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Pros• Making nano patterns without optical apparatus• Making arbitrary patterns by controlling AFM tips• Good linearity allowing excellent line width control• No backscattering which exists in EBL• No proximity which exists in EBL

Cons• Low throughput: serial scan and low speed• Small scan area• Requires higher incident electron dose than EBL

Pros & Cons of SPL (AFM Lithography)

Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Scanning Probe Lithography (SPL)

Atomic Force Microscopy (AFM)

Scanning Tunneling Microscopy (STM)

Scanning Probe Parallel Lithography(SPL Array)

Dec. 10th. 2008Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

1D tunneling

Dec. 10th. 2008Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

STM Lithography

Dec. 10th. 2008

• Application of voltage pulse between tip and sample• “Pushing” atoms• Advantages of STM Litho- Information storage devices- Nanometer patterning atoms

M. Crommie (UC Berkley), Vol. 262, Science, 1993Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Scanning Probe Lithography (SPL)

Atomic Force Microscopy (AFM)

Scanning Tunneling Microscopy (STM)

Scanning Probe Parallel Lithography(SPL Array)

Dec. 10th. 2008Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Scanning Probe Arrays Lithography

Hensy Gandjar, Yuki Takagi, Naoki Matsuzuka, Yoshitada Isono, IEEJ, 2008Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Scanning Probe Arrays Lithography

Mar. 9th. 2009 Rho, Jun Suk

Hensy Gandjar, Yuki Takagi, Naoki Matsuzuka, Yoshitada Isono, IEEJ, 2008

Group I.P.ODec. 5th 2007

Comparison

Strength Weakness

All SPL •Nanoscale Resolution•Accurate alignment•Real-time imaging•Array operation

•Low throughput in serial•Lack of controlling array

STM •Higher resolution (atomic)•Minimum proximity effect•Precise control

•Vacuum control•Limited resist thickness•Limited pattern uniformity•Conducting substrate required•Very low processing speed

AFM •Good reproducibility•Wide range of materials•Precise control•Compatible with self assembly

•Limited pattern uniformity•Debris formation in scratching•Low tip life time in scratching•Array synchronization(DPN)

Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007

Conclusion

Although Several basic issues are still unresolved with respect to these techniques, (i.e. the details of The mechanism of ink transport in DPN are still unclear), it is very promising and developing technique.

Dec. 10th. 2008

On-wire Lithography

Polymer Pen Lithography

SPL with NSOMSPL with SECMSelf Assembly Monolayer (SAM)ETC

Mar. 9th. 2009 Rho, Jun Suk

Group I.P.ODec. 5th 2007Dec. 10th. 2008Mar. 9th. 2009 Rho, Jun Suk